Abstract
Cry1Ac transgenic sugarcane provides a promising way to control stem-borer pests. Biosafety assessment of soil ecosystem for cry1Ac transgenic sugarcane is urgently needed because of the important role of soil microorganisms in nutrient transformations and element cycling, however little is known. This study aimed to explore the potential impact of cry1Ac transgenic sugarcane on rhizosphere soil enzyme activities and microbial community diversity, and also to investigate whether the gene flow occurs through horizontal gene transfer. We found no horizontal gene flow from cry1Ac sugarcane to soil. No significant difference in the population of culturable microorganisms between the non-GM and cry1Ac transgenic sugarcane was observed, and there were no significant interactions between the sugarcane lines and the growth stages. A relatively consistent trend at community-level, represented by the functional diversity index, was found between the cry1Ac sugarcane and the non-transgenic lines. Most soil samples showed no significant difference in the activities of four soil enzymes: urease, protease, sucrose, and acid phosphate monoester between the non-transgenic and cry1Ac sugarcane lines. We conclude, based on one crop season, that the cry1Ac sugarcane lines may not affect the microbial community structure and functional diversity of the rhizosphere soil and have few negative effects on soil enzymes.
Highlights
Controlling plant diseases and insect pests by traditional breeding and modern genetic breeding is the key to achieving food security
The results suggest that there is no exogenous gene shifting from the transgenic sugarcane lines to the rhizosphere soil microorganisms
Though significant difference of the bacteria diversity was found, no significant difference of the actinomyces and fungi diversity was observed in the interaction effects between the sugarcane lines, regardless of whether the line was cry1Ac sugarcane or nonGM (Table 2)
Summary
Controlling plant diseases and insect pests by traditional breeding and modern genetic breeding is the key to achieving food security. As a result of the typical feeding behavior of the larvae that bores into the sugarcane stem, agrochemical control usually spraying insecticides and toxic pesticides on a sugarcane field 5–7 times during a single growing season, which is expensive and potentially harmful to the environment (Arencibia et al, 1997; Chailleux et al, 2013). Breeding for resistance as an approach to stem borer management in sugarcane confers advantages such as inherent control and a low pest density in the field (Kfir et al, 2002). Introduction of the cry1Ac gene was shown to be an effective and economic strategy to improve the borer-resistance of sugarcane (Srikanth et al, 2011), to genetically modified (GM) soybean (Glycine max) (Valderrama et al, 2007; Karthikeyan et al, 2012), cotton (Gossypium hirsutum) (Torres and Ruberson, 2006), corn (Zea mays) (Dutton et al, 2003), and other crops (Valderrama et al, 2007; Gatehouse, 2008; Karthikeyan et al, 2012), which contain Bt genes (cry1Ac, cry1Ab, cry1c, cry3Bb1 etc.)
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